The common mucosal immune system response results in antibody production and cellular immune functions at portals of entry for microbial pathogens. Antibodies elicited by natural infections or induced by vaccines have been demonstrated in mucosal secretions and have been shown to correlate with protection against challenge viruses. Antibodies to human immunodeficiency virus (HIV) have been demonstrated in saliva, semen, colostrum, milk, and in rectal or genital secretions of infected patients. However, the source (mucosal or systemic), isotype, protein targets, and functions of local antibodies to HIV are poorly defined. Because of the possible role of mucosal antibodies in preventing mucosal HIV infection, a better understanding of mucosal immunity is important for developing effective vaccines. Yet, mucosal antibodies are difficult to sample and to measure. We have developed reproducible sampling methods and extremely sensitive protein-specific IgG-, IgA-, and IgM- detection techniques (including enhanced chemiluminescent-immunoblot or "ECL-WB" and enzyme immunoassays or "ECL-EIA") for antibodies cervical, rectal, and salivary secretions. ECL-WB and ECL-EIA will be used to quantitate isotype-specific mucosal HIV antibody responses to denatured or native HIV proteins, respectively. Local antibody titers will be compared with HIV titers and with cellular immune functions (from the collaborative project) in local and peripheral blood compartments to determine the extent and mechanism of immune viral clearance. Local IgG- and IgA-mediated neutralizing antibodies will be measured in patients with recent or long-standing HIV infections against autologous HIV strains from peripheral blood and mucosal sites and against prototype strains to determine the strain-related variability of local functional antibodies. Finally, HIV protein-specific, isotype-specific, and neutralizing antibodies to HIV will be measured in pre- and postnatal cervical secretions of HIV-infected Seattle mothers and in milk samples from African mothers to determine the correlation of antibodies in cervix or milk with intrapartum or neonatal transmission, respectively. These studies will provide a systematic description of the local antibodies elicited by HIV infection. Correlation with local cellular functions and with HIV strain and titer (as determined in the collaborative project) will promote understanding of virus-host interaction via the mucosal immune system.